In Miller U.S. patent application No. Ser. No. 08/294,659 entitled of "Method of Inserting a Balloon Catheter", now U.S. Pat. No. 5,490,838, a balloon catheter is disclosed in which the balloon in its non-inflated configuration has a smooth, cylindrical wall, and is no greater in diameter than the remainder of the catheter. The balloon, in its original form, is a tube made of an elastically expandable, work-hardenable plastic, such as known forms of nylon or polyethylene (polyethylene terephalate).
A stated advantage of such a balloon lies on the fact that as the balloon expands with increasing internal pressure, there is a pressure range which the work-hardening primarily takes place which has an effect of reducing or eliminating the expansion of the balloon with increasing pressure. Thus, if a doctor expands the balloon within a patient to this pressure range, he or she can know with confidence that the balloon diameter is no greater than a predetermined maximum diameter, without the need for a direct observation.
Furthermore, a popular surgical procedure for preventing restenosis in arteries utilizes a catheter dilatation balloon which is surrounded by an expandable tubular stent, for example a wire stent, or an apertured tube stent of the type sold by the Johnson and Johnson Corporation. The balloon and stent are positioned as desired within an artery or other vessel lumen of a patient. Then the balloon is expanded, to expand the stent to a desired configuration. It is desirable to avoid overexpansion from such a balloon as the stent is being expanded.
Conventional arterial dilatation balloons are flexible but not very stretchable, so that they are initially wrapped up in a folded configuration. Disadvantage has been encountered when these balloons are used with stents because of the possibility that, due to nonuniformities in the unfolding, certain portions of the stent become more greatly outwardly pressurized than other portions.
Also, if a stent balloon tends to expand one end or the other first, rather than first in the middle while in the process of expanding the stent, the stent can be driven off the balloon by such asymmetric expansion, so that the stent becomes only partially expanded. This of course can be a great problem during surgery, and may result in the stent becoming positioned improperly in the expanded configuration.
In accordance with this invention, a catheter balloon is provided which can be very narrow prior to inflation, and which can inflate in a circumferentially uniform manner, which is predictably dependent on the inflation pressure, for optimum implantation of stents within the body, and also for other medical uses which are customary for catheter balloons.